The use of light sources, light reflectors and light beams which are either built into a golf club or attached to a golf club, usually along the shaft of the club, are well known in the art and most commonly are employed for visually informing a golfer if the impact face of the club head is square to the target line at the point of actual or imagined golf ball impact.
One such attachment device is disclosed in U.S. Pat. No. 5,467,991 issued Nov. 21, 1995, White, which discloses a base mounting plate which is removably attached to a club shaft and which supports a pair of light emitting diodes (LED's) aimed in opposite directions parallel to the shaft of the club.
As the beam of light emitted from the lowermost LED is offset relative to the axis of the club shaft, the light trace which the beam makes when it impinges the ground is behind the head of the club head. Because of this offset, the light trace on the ground is not representative of the actual location of the impact face of the club head, and further, does not produce a straight line ground light trace in the ball impact area due to the rotation of the hands and club in this area.
The second LED on the White device also emits a beam of light which is offset and parallel to the axis of the shaft, but which in this instance extends in a direction opposite to the first or lowermost beam. This second or upper beam, during the latter part of the back swing, early part of the down swing and during follow through is intended to produce a light trace on the ground which is parallel to the desired target line. While White's golf swing training device is useful in assisting a golfer in determining if the golfer's swing is following the correct swing plane by the two light tracings on the ground, it is not possible through the use of the single and offset downwardly projecting light beam to determine if the face of the club head at the point of actual or imaginary ball impact is on line to the ball, "square" to the ball or if it is open or closed to the ball and which is commonly described as a toe-in or toe-out condition. Toe-in or toe-out of the face of a club head normally imparts to an impacted ball unwanted side spin which results in either a hook or slice.
Cunningham in U.S. Pat. No. 5,470,072 issued Nov. 28, 1995, provides for two spaced apart light sources positioned on the crown or top surface of a club head and which are also positioned in a plane perpendicular to the ball impact face of the club head. If the light tracings from the light sources (which are directed or reflected towards the golfer swinging the club and not the ground) appear superimposed at the point of actual or imaginary ball impact, it indicates to the person swinging the golf club that the face of the club head is square to the ball. However, if the two light tracings in the proximity of ball impact are offset one relative to the other, it is indicative that the club face is not square, and is either in a toe-in or toe-out condition.
Cunningham also discloses the attachment of a bar to a lower portion of the shaft of the club with the bar carrying light sources or light reflectors thereon, and which provides the golfer with the same interpretive information as given when the light sources are positioned on the crown of the golf head.
While Cunningham assists one in determining if the club face is square to the ball at the point of impact, no interpretive visual information is given the golfer about the golfer's swing being in the correct swing plane or if the imaginary ball which appears to be hit square, is in fact being hit square but in a in-to-out or an out-to-in swing arc relative to the desired target line; thereby creating what is termed a "push" or a "pull".